1. Field of the Invention
The present invention relates to a lubrication system and method for a powertrain assembly, and more particularly relates to improved technology for a lubrication system in which lubrication is performed by mechanically scooping up oil accumulated in the lower part of a crankcase, and distributing the scooped-up oil to internal components of the powertrain.
2. Background of the Invention
In Japanese Utility Model Publication No. Hei 05-33686, a known lubrication structure is described, for an engine having a clutch mounted on a main transmission drive shaft that rotates in conjunction with a crankshaft. In the known structure, oil accumulated in the lower part of a crankcase is scooped up by the rotation of a clutch. The scooped oil is then received by oil receivers provided on the inner walls of the crankcase and a clutch cover. The received oil is then supplied, via a flow path, to an oil chamber extending above a transmission system. The oil from the oil chamber drops onto a gear engagement part of the transmission system on the main shaft and a countershaft (a power take-off shaft) via dropping holes formed in the oil chamber, and thereby the gear engagement parts are lubricated. A lubrication structure of this type has been disclosed, for example, in Japanese Utility Model Publication No. Hei 05-33686.
The engine described in the Japanese Utility Model Publication No. Hei 05-33686 is configured in such a way that a crankshaft is movably supported in a crankcase. The rotation of the crankshaft is transmitted to a main transmission drive shaft via engagement of gears and a clutch, and the rotation of the main shaft is further transmitted to a power take-off shaft (a countershaft) via a transmission system.
A lubrication structure is provided in which oil accumulated in the bottom (lower part) of the crankcase is scooped up by the rotation of the above-described clutch mounted on the main shaft, and in which the scooped oil is used to lubricate gear engagement parts of the transmission systems on the main shaft and the countershaft.
More specifically, concerning the lubrication for the gear engagement portion of the transmission system, oil which has been scooped up by the above-described clutch is received by oil receivers provided on the inner walls of the crankcase and a clutch cover and the oil is supplied to an oil chamber via a path.
A portion of the oil supplied to the oil chamber is dropped from the oil chamber onto the gear engagement parts of the transmission systems on the main shaft and the countershaft via a falling hole. In addition, the remaining scooped oil is supplied to the countershaft via a communicating path.
The oil receiver in the lubrication structure described in Japanese Utility Model Publication No. Hei 05-33686, which receives oil scooped up by the rotation of the clutch, is directly formed on the inner walls of the crankcase and clutch cover in the form of a concavity or a groove, and is integrally formed with the case and cover. Accordingly, selection of a structure or shape which has a sufficient oil recovery function as an oil receiver is restricted. Thus, it is desirable to enhance the recovery efficiency of the scooped oil in an oil receiving structure where the oil receiver is formed integrally with a case and cover.
In consideration of the above-described problems, it is desired to provide an improved technology for a lubrication structure in an engine, in which oil accumulated in the bottom (lower part) of a crankcase is scooped up via a rotator rotating in the crankcase and the scooped oil is used to lubricate a gear engagement portion and the like in the crankcase. An improved lubrication technology is one which enhances the lubrication efficiency of the gear engagement portion and the like by enhancing the efficiency of recovering the scooped oil, and which can be provided at low price and with simple structure modification.